Rotary electrical boost device for reducing control forces on airplanes



'Aug- 27,1946 J. s. w. DAvlDsENv 2,406,356

Y ROTARY ELECTRICAL BOOST DEVICE FOR REDUCING l I f CONTROL FORCES ON AIRPLANES f f Filed 'June 16, 1942 INVENToR v E55 Law. av Een l mam y Patented Aug. 27 1946 UNITED STATES PATENTpOFFICE ROTARY ELECTRICAL BOOST DEVICE FOR REDUCING CONTROL FORCES ON AIR- PLANES 3 Claims.

This invention relates to control systems for aircraft and more particularly to a booster control system for aircraft similar to the booster control system described and claimed in my copending application, Serial No. 417,433, filed November 1, 1941.

It is recognized by those skilled in the art relating to aircraft controls to whom this specification is particularly addressed that hydraulically actuated control devices have certain inherent objections when used atextremely high altitudes. Thisl is due to the fact that the low temperatures there encountered cause the fluid viscosity to increase to such an extent that the hydraulically actuated boost devices either become inoperative, `or extremely sluggish in their operatic-n. The regions of todays military operations require booster devices which will be uneffected by the low temperature encountered at these extreme altitudes. The prior artshows that the limitations on these hydraulically actuated devices lhave been acknowledged. The general solution of the `particular problem involved has been an attempt to design a hydraulically actuated device which may be shut off or rendered inoperative, and one which, when made inoperative, offers no additional loads to the pilot. Thus the low temperatures and high viscosity encountered at high altitudes have necessitated shutting off the boost system. My copending application to which reference has been made above is concerned with such a proposition. Notwithstanding the fact that I believethe subject matter of my copending application to be a satisfactory solution in this regard, it is my purpose here to present a control device which will be unaffected by low temperatures, thereby `avoiding the present necessity of shutting off the booster system at these low temperatures thereby also avoiding the present necessity of requiring'the pilot to handle the full control surface loads. To accomplish this purpose I propose to provide a servo-booster device which in its preferred form utilizes electrical energy vto supply the necessary assisting force.

It is an object of this invention to provide a novel booster control system for aircraft, the operation of which is unaffected by low temperatures, and as in the system described in my copending application offers no additional loads to the pilot when shut off or rendered inoperative; and which exerts an assisting force proportional to the pilots manual effort.

It is also an object to provide a booster control system Which will assure that the changes in control reaction will be feltby the pilot to a high degree of fidelity.

It is a further object of this invention to provide a control device which when not in use, or when rendered inoperative, will still function to amended April 30, 1928; 370 O. G. 757) impose aA snubbing'action against suddenly applied external loads such as those which frequently result from kgusts or rough air; and to perform the snubbing action Without loss of feel Y or pilot reaction.

From the standpoint of military vulnerability, the electric powered boostdevice has an advantage over the strictly hydraulic type in that the electric energy can be delivered to the motor through `a plurality of parallel power leads, thus a number of the leads maybe severed without ,affecting the operation of the device,` whereas the strictly hydraulictype is rendered inoperative once its supply line is punctured; It is also recognized that a further simplification from ,the standpoint of military vulnerability or other con'- siderationsvcan be affected by the substitution of an air turbine in place of an electric motor to furnish energy for the rotary boost device. The pressure head required to operate the turbine would, o-f course, be the impact pressure created by the movement ofthe aircraft relative to its flight sustaining medium, and the initial source of energy would be the motoror motors' propelling the craft. Energy is actually stored in the rotating system by reason of its inertia and the fact that the imposed boost loads are of an intermittent nature. 1

It is a further object of this invention, there fore, to provide a booster control system for aircraft which utilizes the kineticenergy of a rotating inertia member to apply a variable and intermittent booster force to aid in positioning the control surface of an aircraft.

Other objects and advantages will become apparent from the specification as the specific features of certain preferred modications of this inventionv are hereinafter described in detail in connection with the accompanying drawing, in which Fig. l is a schematic view of the control mechanism of this invention;

Fig. 2 is an elevational view in cross-section of the rotary power transmitting system, and friction means for transmitting the torque thereof on to said control surface;

Fig, 3 is a cross-sectional plan view taken on line 3-3 of Fig. 2;

Fig. 4 is a cross-sectional plan view taken on line 4-4 of Fig. 2;

Fig. 5 is a schematic view of a modification illustrating a push-pull system of control; and

Fig. 6 is a partial schematic view of a modification wherein an air turbine is utilized to provide a rotary torque to said power transmitting system.

Referring now to the drawing and particularly to Fig. l wherein I have illustratedl a preferred embodiment of this invention in which reference numeral lll designates a control surface of an airend of each of these cables -is secured to the conytrol horn I4 at its opposite ends and lis con nected intermediate its ends to the opposite ends of the protruding arms 8 and9 respectively of the pivoted force transmitting member -i5.- The curely fastened to its respective pistonIB and I9 of the fluid coupling membersindicated generally on the drawing at I6 and I1; Each of these v10h otherend of each of the cables I2 and I3 is s e oted control column 1 is connected by means of Vthe cables 22 and 23 Vto the cylinders 28 and 2| of the -uid couplings. The cable is secured toopposite ends of the pivoted spreader bar 24 intermediate its ends so as to permit any initial rigging tension to be applied at the cable without affecting the uid pressure within the couplings IBand I1. .Y Y

. Flexible fluid pressure hose 28 and 29 lead from the interior of each of the iuid couplings I3 and I1 to the fluid brake cylinders-30 and 3|, respectively. As illustrated in Figs. 3 ande, each of Ythese movable fluid brake cylinders 3l! and 3| key slot formed in each of the supporting members has an arcuate extension 2. This key slot permits relative movement of each supporting member and its torque transmitting member through an angle of 2a. The lugs 62 and `t3 are provided on each of the supporting members and a tension spring 54 is secured to each lug so as to keep the two supporting membersV 45 and 41 in .the'position illustrated in the drawing wherein the key -59 engagesppposite ends of the key slots l The operation of the device, as schematically illustrated in Fig. l, is as follows:

As illustrated in Fig. l, motor 60 is presumed to be rotating in the direction indicated by the arrow B to provide for -rotation of the drum 52 in a clockwise direction when viewed from above and to provide for rotation of the drum 53 inan opposite or counter-clockwise direction as viewed from above by means of beveled gears 5S, 51 and 58, When the operator moves the control column or stick 1 of Fig. 1 in the direction shown by arrow A, tensionV is supplied to the cables 22 and I2.A This tension creates a pressure on the fluidV in the fluid coupling I (i, which is transmitted by the flexible hose 28 to the friction brake cylinder 30.

contain a-pair of oppositely movable pistons. The cylinder 30 contains the pistons 32 and 34 whereasthe cylinder 3I contains the movable pistons 33 and`35. As shown in Fig. 3, each of these pistons 32 and 34 are secured to the free ends 36 and 31 ofthe pivoted and arcuate-shaped brake shoes 38 and 39, whereas the pistons 33 and 35, as shown in Fig. 4, are secured to the free ends and 4I ofthe pivoted and arcuate brake shoes 42 and 43. The outer surface of each of these brake shoes 38 andf39 and 42 and 43 are covered with a suitable brake lining indicated in the drawing as 44. The brake shoes 38 andA 39 are pivotally secured to the friction brake supporting member at 4B, whereas the brake shoes 42 and 43 are pivotally secured to the friction brake supporting member 41 at 48. These brake supporting members 45 and 41 also support the brake cylinders V30 and 3 Iand are each keyed to the spindle portion 49 of Athe torque transmitting member I5 in a manner to be herein-- after more particularly described. The coiled tension springs 50 and 5I retain their respective brake shoes 38 and 39 and 42 and 43 in the position illustrated wherein the respective pistons 32 and 34 and 33 and 35 are each directed inwardly in their respective cylinders 30 and 3 I. i

A pair of brake drums or rotatable members 52 and 53 are supported for rotation on the spindle portion 49 of the torque transmitting member I5 so that flangeV surfaces 54 and'55, respectively, overlie the brake lining 44 formed on the brake arms 38 and 39 and 42 and 43.v The outer edge' of each of these ange surfaces 54 and 55 of the brake drums 52 and 53 are each provided with a beveled ring gear 56 and 51 which meshes with the beveled gear 58 shown splined on the shaft of the motor 60. Rotation of the motor 60,' therefore, produces rotation of the brake drums 52 and 53 in opposite directions as indicated on lthe drawing by the arrows.

As stated previously, the brake arm supporting members 45 and 41 are each secured to the spindle portion 49 of the torque transmitting member I5 by means of a key 59. The keyway or The pressure transmitted to the cylinder 33 acts uponthe pistons 32 andi-X4 to move the brake shoes 38 and 39 and expand the .friction lining 44- against the inner surface of thel ange' 54V of the drum 5 2 which is rotating in a clockwise direction. The friction between the brake band 44 and the drum 52 tends to cause the brake band .44 to rotate with the drumV 52 in a clockwisev direction. The torque thus absorbed by the brake band 44 is transmitted through the brake supporting member 45 and the key 59to the spindle 49 and tends to move the torque transmitting member I5 about its pivot. The motion thus transmitted to the member I5 tends to move the control surface I9 by transmitting the torque applied thereto to the control horn I4 through the force transmission cable I2.

At the time that the brake shoes 38l and 39 were expanded into frictional engagement with the rotating drum 52, the brake shoes 42 and 43 were not expanded into contact .with the rotating drum 53, consequently the brake supporting member 41 is free to follow the movement of the key 59 on the spindle 49 by virtue of the spring 64 which is attached between the lugs 52 and 63 formed on the friction brake supporting members 45 and 41. This spring action serves to keep the driving face of the keyways 6B and 61 against the key 59. It should be noted that the assisting force of the brake shoes 38 and 39 operates with respect to the drum 52 and can be smooth and proportional to the tension applied to the cable 22 the same as is the deceleration of an automobile equipped with hydraulie brakes smooth and proportional to the foot pressure exerted by the operator.

in a direction opposite to the direction indicated by the arrow A relieves the friction pressure on the drum 52 and increases the friction pressure on the drum 53, which tends to assist the control 4 fluctuations will cause the fluid pressure within the `fluid couplings I 6 and I1 to vary andwill Movement of the control stick 1v tive brake drum 52.

i 5. thuscontrol the boostforces applied to the-control. surface.v Of course, any variations in fluid pressure in the fluid couplings wil-Lbe felt by l the operator in a reduced ratio which is fixed by the design of the. unit.

In the event that a boosted forceis not desired, the energizing circuit of. the electric motor Ellis disrupted and the driving torque producing con-- tinuous rotation of the brake. drums 5,2, `and k53A is removed. Under these conditions, which may result. from a. power failure,V it is desirable that` additional loads, beyond the normalcontrol sur-- face loads, should not be imposed upon the pilot or,- interfere in any way with the successful, ordi nary -positioning of the control surface.n Asshown in Figs. l and 2, arms8 and 9. of the torque transmitting member I are. secured to the control cables I2 and I3 and in all cases move with the cables. As it .was initially proposed that the. operator move the control stick 4in thefd'i'rection indicated by the arrow A, the applied. force goesA tothe fluid coup-ling IE increasing the fluid pres` sure therein and also pulls directly on the cable I2 and control horn I4 tending'to move the. control surfacel.- The increase in: fluid pressure at I6 if the applied force is suilcient will be transmitted to the brake cylinder 3Il causing the. brake shoes 38v and 39 to move forcing the brake lining 44 into frictional engagement with theinner surface of the flange 54 on the lorakelY drum` 52 thus locking the brake drum 52` to thebrake supporting member 45.v The lug `62' whichis se cured. to the brake supporting member 45' can not move because ofthe frictional. engagement between the supporting member and the inopera- However, the brake shoes 42. and 4'3 are controlled by the fluid pressure. within the fluid coupling I'Il which is not under pressure and hence these brake shoes will not be forced into frictional engagement with the interior surface 55 of the brake drum53. Therefore, inmoving the control column 'I inthe' direction A, the spindle 49 ofthe torque transmitting member I5 will be moved in a clockwisedirection and is free. to so move with respect to the brake drum` 52V and brake arms 38 and 39 byreason-.of the ar-v cuate-shaped key slot B6. of. 2a. The fluid. inl the. brake cylinder 3l is not under pressure and the `brake bands 42 and 43. are not forcedinto. frictional engagement with the brake dru'rr'1-l5f3,l therefore, this drum 53 is freev to rotate relative -to the brake arms 42 and 43. Since the key 59' is retained against the edge of the slot, clockwise rotation of the torque transmitting arm I5' will cause the friction brake supporting member 41` to move with the spindle 4'9- andthe operator' has to overcome only the small tensional force of the spring 64 to move'the control surface to the new' position.

'I'he reason that the key slots in the frictional band supporting members 45 and 41" have-an arcuate extension of N' is primarily precautionary, since the angle a is intended to be equivalent to the full movement of the spindle 49 and 6 the control surface produce. piloti fatigue andare undesirable from the standpoint of` control system structure. These'suddenly applied loads frequently arise from gusts or fromy rough` air., In

the modification ofj..my invention..whichifhave Y .illustrated in;Figs.-fI]and 2,.,itmay'bev assumed. that a force producediby' a gust of windissuddenly applied to the control surface in the direction in,- dicated. by the arrow C and the operator resists movement of the. control surface in: said direction by applying a. manual force: to the con-trol stick` 1 inV the direction indicated by the. arrow A. The pressure in the fluid coupling' I6 is thus increased and tends to. lock the. friction-bands: 44 of the brake slices 38 and 39' against. theiinn'er flange surface of the: brake drum 52'. .This brake drum is geared to the' inoperative: electric motor` 69.. Thuis; the, shock load transmitted bythe cable:

I2l tothe spindle 4.9" of "the 'torquetransmitting u membel` .l5 wlfien'N appliedfby thefkey'. 55E/in a; counter-clockwise direction. against the: friction brakeV supporting member 4'5 is snubbed against: u the inertia of the electric motor.

A smallcnn-5 trol force appliedto the: cable 22` is all .thatjirsnecessary to produce the snubbing action.v Vifh-ile: the inertia. of the motor Sil' serves' asn a snubbenl it -is apparent that if the control surfacevtere: actually moved by these eXteriorlyV applied forces;y cable 22 would have to carry the wholev load: 'eXf--l isting on cable. l2..

Fig.. 5 discloses,l a. modification of: this invention: wherein a push-pull system of control is'A used. A single force transmitting elementi HL4 which is;

. illustrated as a Bowden wire, delivers the. push'.-vv

the fluid coupling l I'.

pull pressure transmitted to the control stickl^ mitted by the Bowden. wire l0 through the fluidA within the chambers 'i5 and into the brake cyll inderg 39 and 3l.. The flexible hose 'il '58- conneet the outlet passages leading from the:

fluid-tight chambers 'f5.- and 'IG to the' opposite sides of the piston of the. brake cylinders 3@ and' 3l, respectively. The control rod 'I3'ifs connectied intermediate the ends of the arm 9" of the; pivoted torque transmitting member l5.: and isf movable in the slot T9 of the torque transmitting arm as this arm movesy aboutI the fixed shaft I'. The torque transmitting mechanism, schematically illustrated in this modification, islsiinilar in all respects to that illustrated' in Fig.; y2, and similar reference numerals have been: used tcind-icate'their parts. y

The modification of the invention illustratedin 6 shows the application of' an air turbine Z382 for transmittingA a rotation force: to the two brake drums` 52" and 53. tis intended that the motion of travel of the pistons if: i9* ofthev huid; couplings IS. and Il' wiil be v small. inf

going from an .initial to a. pressure'.- rlhis motion may be. limited. by providing stops, on. the inner: surface of the cylinder, 'as-'illus trated, which Serve to transmit .the forces. ape plied to the control column 'I on to the control horn I4, in the event of loss of fluid within the ui-d couplings. In the modifications illustrated, the ratio of the total force including the assisting force plus the manual forcev as transmitted tothe controlsurface l by either of the cablesV I2 or I3, to the manually applied vforce to the cables 22 or 23 is not variable bythe operator as it is in the copending application but 'ison the -contrary xed by the particular design. It shouldv be apparent, however, `that 'suitable mechanical the scopev of this invention. As a specific example,

a uid pressure switch could be installed which would energize 'thefmotor only when' the.- initial uid pressure in the couplings had risen to acer tain desired value. only when torque was desired. It is also apparent that the small beveled Vgear vcan be connected'to the/motor Ybymeans of a uni-directional clutch so that the motor would deliver/torque in only one direction. This would', permit the brake support-Y ingunit to be connected directly to the spindley 49 of the torque transmitting member l5.,v With this arrangement, it would benecessary to rctate Ythe drums 52 and 53v as well as the small beveled gear in the event of failure of the power system. It is also apparent that a single drum could be rotated by an electric motor, the direction of rotation of which would be controlled by Thus, the motor would-run member for each -of Asaid drums, Y each' saidfplate member including an Varcuately-shaped keyway for Vcooperation withsaid key, said keyways ex! tending in opposite Vdirections from said key, means carried by each of said platemembers `to frictionally coupleit tothe drum member Lasso- Y ciated therewith, resilient means interconnect-f ing said plate members in such manner as to hold the driving face of each of said keywaysagainst said key, andfmeans' connected in said 'manual force Vtransmitting means' for actuating said fric# tion coupling means.

2. In a device for supplying a boost force to aid in positioning the control surface of anaircraft, the combination comprising, manually' actuated means for transmitting a manual force to said control surface to effect motion thereof, fluid coul pling ,means' included .in said manually actuated means, a spindle, ra key carried by saidfspindle,

-meansrconnectin'g said .spindle in` vsaid manual force transmitting`means 1305111101015 said boost force to saidcontrol surface upon rotation of said spindle, a pair of drums mountedY to rotate on said spindle, means for rotating saiddrums in opposite directions, a plate member foreach of said drums, eachrsaid plate member including an arcuately-shaped keyway for cooperation with saidvkey, said keyways extending in opposite directions from said key, means Ycarried ,by each of said1plate members to vfrictionally couple it to the drum'member associated therewith, resilient the individual fluid couplings, particularly if the Y torque were to be transmitted to the spindle 49 through friction discs because the friction discs work equally well in either direction Whereas the brake bands disclosed, operate better in the manner illustrated. The disc type of clutch unit may be preferred under certain circumstances to the type illustrated inthe drawing since an inherent advantage of the disc is that they are practically free from grabbing actions in changing atmosphere conditions, thus assuring smooth uniform assistance. VThe particular disc type of clutch to which VI have referred are well known to the art and are yused as brakes on aircraft. The invention herein disclosed may thus be practiced otherwise than specifically described or illuS-,y

trated and still remain Within the scope of the appended claims.

The invention described hereinmay be manufactured and used by and for the Government of the United States of America for governmental purposes Without the payment of any royalties thereon or therefor.

1. In a device for supplying an assisting force to aid in positioning a control surface of an aircraft, the combination comprising, manually actuated Ymeans for transmitting a manual force to said control surface to effect motion thereof, a spindle, a key carried by said spindle, means connecting said spindle in said manual forcetransmitting'vmean's to supply said assisting force upon rotation of said spindle, a pair of drums mounted to rotate on said spindle, means for rotating saidV drums in opposite directions, a plate means interconnecting said plate members in such manner as to hold the driving face of the' keyways in said platevmembers against said key,

fluid motor means for actuating said friction coupling means, and conduit means connecting said uid motor means to said fluid coupling means'.

3. In a device for supplying an assi-sting force to aid in positioning a control surface of Van aircraft, the combination of afpivoted control surface, means for transmitting a manual force to actuate said control surface, a piston and cylinder interposed in said force transmitting means, a spindle, a key carried thereby, an arm secured to said spindle, meansl connecting' said arm in said forceV transmitting meansV to supply said asv Asisting force to said control surface, a. pair `'of drums rotatably mounted on saidv spindle, means for rotating said drums in oppogsitedirections, a plate member foreach of said drumsfsaid plateY members being journaled onY said spindle, a key# way in each vof, said 'plate members vwider than the key carried bysaid spindle means connecting Isaid plate members in such manner as to hold the driving face of the keyways therein against said key, means carried byeach of said plate` members for frictionally, couplingY said jdrum members thereto, hydraulicV means to actuatel said couplingmeansand conduit means connect-V ing said hydraulic means to saidY cylinder, whereby upon application of manual force the increasedv pressure in said cylinder will cause said hydraulic means to actuate said frictional coupling means to thereby transmit a portion of the inertia of one of said rotating drums into saidforce trans#L mitting means through its associated plate meniber, spindle and arm to supply, said assisting force. Y. l

Y vJESSS. DAVIDSEN. 

